feat(plugins): load and validate plugin manifest.json

.devcontainer/devcontainer.json

app/Config/Validation.php

app/Helpers/rss_helper.php

app/Validation/OtherRules.php

modules/Admin/Language/en/Validation.php

modules/Plugins/Commands/UninstallPlugin.php

modules/Plugins/Config/Services.php

modules/Plugins/Controllers/PluginController.php

modules/Plugins/Core/BasePlugin.php

modules/Plugins/Core/PluginInterface.php

modules/Plugins/Core/Plugins.php

modules/Plugins/Helpers/plugins_helper.php

modules/Plugins/Manifest/Author.php

modules/Plugins/Manifest/Manifest.php

modules/Plugins/Manifest/ManifestObject.php

modules/Plugins/Manifest/Settings.php

modules/Plugins/Manifest/SettingsField.php

modules/Plugins/Manifest/schema.json

themes/cp_admin/plugins/_plugin.php

themes/cp_admin/plugins/_settings.php